1. Field of the Invention
The present invention relates to an engine start control system.
2. Description of Related Art
Recently, vehicles, which have a system that enables engine start without using a key, are well marketed. For example, in a system called as “Smart Entry & Push Start System”, unlocking of a vehicle door and authenticating of an ID are performed through radio communication between a portable radio communication device, which is carried by a user, and a radio communication device (a transmitter and receiver device) of the vehicle. When the user gets into the vehicle and pushes a push switch of the vehicle while depressing a brake pedal, the engine is started. In this case, as shown in FIG. 12 of Japanese Unexamined Patent Publication No. 2004-324469, when a detection signal, which indicates detection of depression of the brake pedal, is absent, i.e., when the brake pedal is not depressed in the normal time, the engine is not started even upon depression, i.e., push of the push switch. This is implemented by the engine start control flow disclosed in Japanese Unexamined Patent Publication No. 2004-324469.
In the above push switch type engine start system, an output of a brake sensor (e.g., a switch for lighting a stop lamp of the vehicle), which detects the depression of the brake pedal, is often used as the detection signal that indicates the detection of the depression of the brake pedal. However, in a case where the brake sensor or its wiring fails, even when the brake pedal is depressed, the detection signal is not outputted from the brake sensor, so that the engine cannot be started through use of the push switch.
Furthermore, many vehicles have a mechanism, in which a brake booster is provided in a hydraulic circuit of a brake system to assist a brake pedal operation of a driver and thereby to increase the applied force, which is applied onto the brake pedal. In one exemplary case, the assist power of the brake booster uses a negative suction force, which is generated in an intake manifold of the engine. When the engine is stopped, the remaining negative pressure, which remains in the brake booster, gradually leaks, so that the substantial assist force cannot be made. The leakage of the negative suction force is increased when the brake pedal is repeatedly depressed by the driver. As a result of the pressure leakage, the brake pedal becomes stiff, i.e., becomes difficult to depress in comparison to the normal time, at which the brake pedal can be easily depressed by the foot of the driver to start the engine. Thus, even when a relatively large force is applied from the foot of the driver onto the brake pedal, the brake pedal cannot be depressed to a predetermined stroke, at which the brake switch is urged by the brake pedal to output the detection signal. Therefore, even when the brake switch is normal, the engine cannot be started.
A fail-safe mechanism of the brake switch against burnout, breakage of wiring or any other failure of the brake switch has not been implemented or considered since the brake switch has not been in cooperation with a main part of the engine start electronic system and has been previously used only as a switch for lighting the stop lamp of the vehicle. However, the disablement of the engine start poses serious problems to the user. Specifically, when the engine cannot be started, the user cannot drive the vehicle to an automobile dealer or a repair shop and also cannot operate an air conditioner of the vehicle. In an extreme case, the vehicle needs to be towed by a wrecker car.